Many interns, residents, and even attending staff who perform acute care services (i.e., trauma/transplant surgery; neonatal, pediatric, adult ICU, anesthesia, or emergency room care) routinely work 24 or more hours continuously. The nonmedical press has attributed a deterioration in acute care services to such long work hours. While it is clear that after some period of time long work hours result in a deterioration of quality of care and are a hazard to both patients and providers, data do not exist to document when such a deterioration of quality of care begins or length of continuous on-duty periods after which simple activities of life, such as driving home, become a hazard to the care provider. Our object is to determine the extent to which psychomotor function has deteriorated in anesthesia and surgical personnel who spend the night on call, to determine when performance deteriorates (specifically 24 hours or 36 hours after call), and to determine any residual effects upon return to duties following a night on call and a night of rest. The effect on psychomotor function of age, number of years after medical school, position in the medical hierarchy (attending, CRNA, or resident), length of time spent on duty or sleeping before starting the call (clinical day beginning at 7:00 a.m. or 4:00 p.m.) and amount of sleep time spent on call, will be examined. We will compare our results with psychomotor function changes after alcohol to allow for more informed calibration when political-social-economic judgments restricting work time are made.